AN unlikely engine-building alliance between BMW and Peugeot-Citroen is set to slash the cost of business motoring when ‘leapfrog technology’ is unveiled in the next 12 months.

Developed to fit under the bonnets of at least 20 top-selling hatchback, saloon and estate models from BMW, Peugeot and Citroen, the new P-series power units are claimed to herald the biggest advance in petrol technology in a decade.

The German-French collaborative motors promise up to 15% better economy with higher performance and significant reductions in Co2 exhaust emissions and servicing costs for cars ranging from the MINI to the Peugeot 307 and Citroen C4.

Peugeot Citroen chief engineer Francois Bordes said: ‘We have created a world leading package. These engines will be unrivalled in the marketplace and are so efficient that I believe we have effectively cut the benefit gap between diesel and petrol power by 50%.’

Due to be in production in the PSA plant in Douvrin, France, by the end of 2005 and at Hams Hall, the BMW engine factory near Birmingham 12 months later, the P-series family will come in 1.4-litre and 1.6-litre capacities.

Aimed at following the 'downsizing' trend set by the French group’s latest HDi turbodiesels, the newcomers have been honed to blend class-higher output with category-leading performance and economy.

BMW Group chief engineer Johann Schopp claimed: 'In every application, P-series is more compact than the engine it will replace. Significantly, it is also lighter thanks to a combination of intelligent design and innovative materials and will offer clear advantages to the customer in terms of driving dynamics.'

Available in either normally-aspirated form with variable valve timing or with turbocharging and direct injection, the P-series represents a big step by both groups toward reducing overall fuel consumption in order to reach the fleet CO2 target of 140g/km by 2008.

Designed to span a 75bhp to 170bhp power band and intended only for mounting transversely in front wheel drive applications, the units are seen as a benchmark in demonstrating how the high-grade engineering solutions needed to meet increasingly stringent emissions regulations can be more cost-effective.

Company officials declined to reveal roll-out details when the new range was announced at the BMW Research and Innovation Centre in Munich, but it is understood that 115bhp and 143bhp versions of the 1.6-litre motor will be first in the showrooms to take over from current two-litre PSA units.

At present, BMW has no plans to use the engines in any model-line other than the Mini, but both displacements will be on offer by the time the next-generation range starts coming off the lines at Oxford in 2006.

In normally aspirated form, the 1,598cc unit develops 118 lb-ft of torque and this is the motor that will drive the Mini Cooper. With a healthy 177 lbs-ft torque available from only 1,400 revs, its turbocharged stablemate promises to be well suited to the Cooper S, although it is likely that a higher-output version will also become available in due course.

Under the collaboration plan launched two years ago, annual output of the P-series will run at around one million units, but while each production site will have a daily capacity of 2,500, Peugeot and Citroen cars should account for 80 per cent of planned volume.

PSA Peugeot Citroen chassis and powertrain engineering vice president Norbert Lartigue said: ’I don’t know who suggested we got together over this, but I think the outcome is great for both partners. We each needed a new generation of compact performance engines and the result is a win-win situation – we have established the right balance between cost and benefit and these engines will be the leaders in their sectors.’

The new engine family boasts a world first in featuring a water pump that saves fuel. A special servo motor disengages the belt drive during cold starts and brings the pump into action only when normal operating temperature is reached. As a result, the engine warms up faster, heater efficiency is improved and emissions are reduced.

Weight has been reduced with the use of a unique aluminium crankcase and a flow-controlled oil pump improves fuel consumption by one per cent.

Performance and economy details will differ with each application, but all P-series powered cars will have 20,000-mile oil service intervals and will be able to cover 40,000 miles before spark plugs and air filters need to be changed. The engine’s timing chain is maintenance free and valve adjustment is automatic.

P-series fact file

All engines have twin chain-driven composite camshafts and 16 valves. Variable valve drive version: Compression ratio 11:1, output 115bhp @ 5,750 revs, 118 lb-ft torque at 4,250 revs. Turbo version: Compression ratio 10.5:1, output 143bhp at 5,500 revs, 177lb-ft torque at 1,400 revs.